Buffer safety stop



April 25, 1933. J. DUNLOP 1,905,273

BUFFER SAFETY STOP Filed Aug. 8, 1930 2 Sheets-Sheet 1 x O I Caz a: 45 Cw A v /0 a 9 "d" Ea Ea i N V E N T O R James flu/ilop April 25, 1933.

J. DUNLOP 1,905,273

BUFFER SAFETY STOP 2 Sheets-Sheet 2 Filed Aug. 8, 1930 lNVENTOR James Dun/op ATT'ORNEY Patented Apr. 25, 1933 UNITED STATES PATENT C JAMES DUNLOP, OF PARK RIDGE, ILLINOIS, ASSIGNOR T WESTINGHOUSE ELECTRIC ELEVATOR COMPANY, A; CORPORATION OF ILLINOIS BUFFER SAFETY STOP Application filed August 8, 1930. Serial No. 473,916.

My invention relates to safety systems for elevators and more specifically to systems for preventing the continued upward movement of either a car or a counterweight followed by the subsequent falling back of such body and consequent snapping of the cables when thedescent of the other body has been suddenly retarded.

When an elevator car is moving downwardly at a sufficiently high rate of speed to trip the car safety device and the safety device is set, the counterweight, which has been ascending, does not stop as suddenly as the car, and, by reason of its momentum will continue to ascend, .lifting the compensator sheave with it by pulling up the compensator cables. The hoist cables will then become slack, and, when the counterweight stops by gravity and starts descending, it

will draw the hoist cables taut with a snap which is apt to break them or pull them loose from the counterweight or the car.

If, while traveling in the opposite direction, the descending counterweight is caught and stopped suddenly, the car will continue to travel upwardlyfor a short. time after the counterweight has stopped. The continued upward movement of the car will cause a slack condition in the hoistcables adjacent thereto and, when thecar stops by gravity and starts to descend, the cables will be drawn taut with a snap which is apt, to break them or pull them loose from the car.

Such conditions will occur whenever either descending body is suddenly stopped by anything, such as the application of a safety device, and areespecially dangerous in high-speed. elevator systems.

It is, accordingly, an object of my invention to provide means for checking the up ward movement of the counterweight or the car when the descent of the other body has been suddenly retarded, and thereby obviating the condition of slack cable before it occurs. e V

It is a, further object of my invention to provide a device for taking up any slack It is also an object of my invention to provide means for retarding the downward motion of the elevator counterweight if 'a slack condition of the hoist cable should occur from any cause whatever. V g

In accordance with my invention, the compensating sheave is attached to a buffer cable passing under an idler pulleymounted rigidly on the bottom of the hatchway and 1,

thence extending upwardly to the plunger of the buifer. V

The buffer, therefore, acts to check the upward movement of the compensating sheave and prevents the condition of slack cable by checking the continued upward movement of either the, car or the counterweight, after the descent of one of the bodies has been suddenly retarded.

As an additional safeguard, I may provide a slack cable take-up device to be carried by the car, for taking up any slack that might occur in the hoist cable above the car.

A snubber may be provided, on the counterweight, for snubbing the guide rails to prevent the rapid falling back of the asso ciated body in the event that'the hoisting cable should ever go slack from any cause whatever.

My invention, bothas to its organization and its method of operation, together with additional. objects and advantages thereof, will best be understood from the following description of a specific embodiment, when readin conjunction with the accompanying drawings, in which Figure 1 is a diagrammatic view representing an elevator safety system equipped in accordance with my invention.

Fig. 2' is a detailview. of the slack-cable take-up device represented diagrammatically onthe elevator car in Fig. 1. V Fig. 3 is a top plan view of a slack-cable take-up device, the top plate and pulley being removed, as indicated by line IIIIII in Fig. 2. 7

Fig. '4; is a. similar viewrof a slack-cable take-up device but showing thetop plateand pulley in place. T

Fig. 5 is a sectional view taken on section line V-V of Fig. 2.

Fig. 6 is a view, in side elevation, of the guide-rail snubbing device which may be carried by the counterweight or by the car in the elevator system shown in Fig. .1.

Fig. 7 is a view, in side elevation, of a modified form of snubbing device mounted in the cross-head, showing one side of the cross-head member cut away.

Referring to the drawings, I have shown, in Fig. 1, an elevator car G supported by hoist cables Ca and counterbalanced by a counterweight Cw, in the usual manner. The hoist cable Ca passes around a hoist sheave S which may be actuated and controlled in any well known manner. A compensating cable 1 passes under a compensator sheave 2 which is suspended near the bottom of the hatchway. The usual buffer 3 is mounted on the bottom of the hatchway.

In accordance with my invention, a buffer cable 5 is provided to pass under anidler pulley 6, which is rigidly mounted on the bottom of the hatchway, and to extend upwardly therefrom, one end being secured to the compensating sheave 2 and the other end being secured to the movable plunger 7 of the buffer 3. An independent bufi'er cable may be attached on each side of the compensator and buffer, each cable passing through a separate idler pulley, in order that a balanced condition shall at all times prevail. Hence, it is to be understood that there are two bufier cables 5, although only one is visible in Fig. 1.

The buffer cables 5 may be attached to the compensator sheave by means of guide memhers 8 supported vertically in brackets 9 secured to the hatchway Walls (not shown). The upper, end of each guide member is provided with a stop 10 which will engage the stationary bracket 9 and limit the downward motion of therguide member. Each guide member 8 passes freely through a groove 11 in. the side of the compensator sheave. At anintermediate position along each groove, a cavity 12 is provided having an inclined cam' surface 13 which extends angularly away from the'groove'. A hardened steel, roll 14:, which has a bifurcated peripheral surface, is carried in the cavity. It will be apparent that the shape of the cavity is such that the steel rolll i will normally rest against the guide member 8 and engage the latter to prevent movement of the sheave 2 upwardly with respect thereto; Movement of the sheave 2 downwardly, with respect to the guide'member 8, may occur freely, however, with the result that any slack caused by stretching of the hoist cables and the compensator will be automatically taken up at all times.

As an additional precaution, the hoist.

ably through a partition member 20 where the other end of the rod terminates in a head 21. A'compression spring 22 is provided on the rod 19, in concentric relation thereto, and is compressed between the partition member 20 andthe head 21 of the rod. It will be apparent that the spring 21 introduces a force whichltends to move the pulley 16 toward the partition member. 20. This force is'normally resisted by the tension of the hoist cables Ca caused by the weight of the car C. Ifthetension on the cable Ca is released for an instant, the spring 21 will move the pulley16 toward the left, thereby drawing up the slack around a stationary idler pulley 2 1. In order to prevent the pulley 16 moving back to its normal position when the tension of the cable Ca is resumed, a suitable latch or pawl 25 and cooperating rack gear 26 are provided, as shown in Fig. 2. V V

The stationary idler pulley 24 may be pivotally mounted ahove'the cross-head between a pair of brackets 27 mounted on the top plate 28. as shown in 5. The idler pulley 24 serves to increase the amount of slack cable that will .betaken, up by a given movement of the movable pulley 16' and prevents the shiftingof the suspension point and consequent unbalancing of the car when the device operates. v

As, an additional safeguard, the hoist cable Ca may, at its point of attachment with an elevator body, such as the counter} weight Cuabe associated with a guide-rail snubbing device similar to that shown in Fig. 6 or that shown in Fig. .7 The purpose of this device is to prevent therapid falling back of thebody, with a consequent snappingof the cables, if, in some manner, slackscable should occur in spite of the other safeguards provided.

As shown in Fig. 6, the snuhbing device may comprise a pair ofrail-gripping aws,

them in cooperative relation to the various T; f

adjacent elements. A compression spring 38 is mounted concentrically on each actuator 37 where it continuously exerts. a thrust between the rigid bracket 36 and the wedge 37 which tends to move the wedge into engaging relation to the innermost extremities of the rail-gripping jaws 34.

The wedges 37 are of such shape that, when interposed between the inner extremities of the rail gripping jaws 34 by the springs 38, they will force them apart and thereby urge the outer extremities of the jaws together to grip the guide rails 47 and 48. The springs. 38 are normally retained in compressed condition by a yoke-shaped retaining bar 42 the extremities of which engage the rollers 39 and hold the actuators 37 toward their innermost or inelfective positions. The extremities of the yoke member 42 which engage the rollers 39 constitute cam-like surfaces having diverging portions, as shown in Fig. 6.

The hoisting cables Ca: pass through-the cross-head 45 of the counterweight Cw and are attached to the yoke-retaining member 42 in any suitable manner. The weight of the body is then supported by the upward thrust of the yoke member 42 upon the' lower side of the cross-head 45.

Suitable springs are provided to bias. the yoke member 42 away from the cross-head 45. As shown, compression springs 46 are disposed concentrically on the cables Ca and are compressed between the upper surface of the yoke 42 and the lower surface of the cross-head 45.

In the event that the cables Cw become slackened or the tension thereof becomes less than a certain predetermined amount, depending upon the strength of the biasing springs 46, the yoke 42 will move away from the cross head, and the rollers 39 will move outward along the diverging surfaces thereof. The actuators 37 will be moved, by springs. 38, into engagement with the railgripping jaws 34 which will grip the guide rails 47 and 48 to retard the movement of the counterweight. V

In Fig. 7 a modified form of take-up device is shown wherein the various elements of the device are similar to those shown in Fig. 6 but are disposed within the upper cross-head member. In this arrangement, the brackets 36 are secured to an upper plate 51 which is. bolted to the upper side of the cross-head 45. I

My invention is best understood, however, when considered in connection with an assumed operation. Let it be assumed that the elevator car C, represented in Fig. 1, is V descending at full speed. As the car travels down the hatchway, it may be suddenly retarded at a rate greater than that'caused by gravity, by an application of the car r safety device or by some other means.

When the car is suddenly retarded at a rate greater than that caused by gravity, the counterweight Cw tends to continue traveling upward for a short interval of time.

In traveling upward, after the car has stopped, the counterweight must pull up one end of the compensator cable 1 and lift the 1 the condition of slack cable is obviated before it occurs.

If, because of stoppage of the motor or some other condition, slack cable has occurred above the counterweight Cw, the

snubber carried by the counterweight will operate to grip the rails and prevent the counterweight falling back. A similar railsnubbing device may also be'carried by the car, if desired, instead of the slack-cable take-up device.

When the elevator is operating in the opposite direction, the car will be ascending and the'counterweight descending. If the counterweight should happen to be suddenly stopped in any manner, as by'striking a buffer or by the setting of its safety device, the car would tend to continue upward, therebycreating slack in the adjacent hoist cable. The car couldrnot continue upward, however, without also lifting the compensating cable 1 and sheave 2. As previously set forth, cables 5 are attached to the compensating sheave 2, passed under idler sheaves 6 on the bottom of the hatchway and extended upward to the plunger 7 of the buffer 3. Hence, the rate at which the compensator sheave 2 may be lifted is limited by the buffer which, therefore, actsto check the upward movement ofthe car and the formation of slack cable.

It will, therefore, be seen that I have de vised a system which will prevent the continued upward movement of either the caror the counterweight and the consequent falling back of the body, thereby snapping the cables, after the descent of the other body has been suddenly retarded. Furthermore, I have provided various slack-cable take-up devices'and snubbing devices on the car and counterweight to take up any slack cable that may occur and to prevent'the falling back of the body in the event that the cables should go slack.

Although I have shown and described certain specific embodiments of my invention, I am fully aware that many modifications thereof are possible. My invention,

therefore, is not to be restricted except in so far as is necessitated by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. The combination with an elevator system comprising an elevator car, a counterweight, a hoist cable connected between the car and the counterweight and passing over a hoist sheave above the hatchway, a compensating cable connected between the car and the counterweight and passing through a compensating sheave suspended on the compensator cable at the bottom of the hatchway, and a bufier mounted on the bottom of the hatchway, of a buffer cable connected to the compensator sheave and to the plunger of the buffer, and a rigidly mounted idler pulley mounted on the bottom of the hatchway for receiving the cable as it passes from the compensator to the buffer, whereby an upward movement of the compensating sheave will cause a corresponding downward movement of the buffer plunger.

2. The combination with an elevator system comprising an elevator car, a counterweight, a hoist cable connected to the car and to the counterweight and passing over a hoist sheave above the hatchway, a compensating cable connected to the car and to the counterweight and passing through a compensating sheave suspended on the compensator cable at the bottom of the hatchway, and a buffer mounted on the bottom of the hatchway, of a bufier cable having one end thereof attached to the plunger of the buffer and the other end attached to the compensating sheave through a device which prevents movement of the sheave in one direction relative to the end of the cable but is not effective to prevent such relative movement in the other direction, and a rigidly mounted idler pulley for receiving said bufi'er cable as it passes from the sheave to the buffer, whereby an upward movement of the compensating sheave will cause the buffer to be depressed, thereby limiting the upward movement of the compensating sheave.

In testimony whereof, I have hereunto subscribed my name this 31st day of July,

JAMES DUNLOP.

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